1. Field of the Invention
The field of art to which this invention pertains includes operator controls for vehicles and, more specifically, a steering control for a vehicle.
2. Description of Related Art
The customary operator control device for steering wheeled vehicles is the steering wheel. The steering wheel provides a means of continuous operator input to the control and a means of amplifying operator input force, at the wheel rim, to the steering system. On some vehicles, such as certain lift trucks, limited space for mounting and operating a steering wheel and other considerations, make the use of a joy stick or lever advantageous as a steering control. Full power steering systems, with the vehicle steering system providing amplification of the force and motion of the operator control necessary to steer the vehicle, require that the operator exert only relatively small forces and limited motion necessary to drive a transducer, sensing control position.
A second function of continuous input control devices, such as the steering control, is the provision of support for the operator in resisting the forces acting on the body as a result of speed and direction changes of the vehicle. This is particularly important to the standing operator because of the height of the body's center of gravity and the lack of any secondary means of support, such as friction between the body and the seat.
All forces must be reacted through the arms which are engaged in the operation of the steering control and, on many vehicles, another device controlling speed of the vehicle's movement. The joy stick, as illustrated in U.S. Pat. No. 3,669,465, levers and steering wheels provide little support for the operator in the direction of intended control movement because the force required to actuate the control is kept purposely low and the point of application of force, the hand grip, is displaced from the axis about which the hand grip rotates. As a result, any attempt by the operator to stabilize the body may cause unintended vehicle movement.
The relatively high forces applied to the control by the operator makes it necessary to isolate these forces from the fragile transducer used to sense control position. Precision bearings and machined surfaces can be used to control relative movement of the transducer and the elements of the control engaged by the operator. A flexible mounting bracket; as illustrated in IBM Technical Bulletin, Volume 25, Number 8, January, 1983; provides a means of limiting forces on a rotary transducer, such as a potentiometer, subject to practical limitations for material thickness and bracket shape and size but imposes significant costs for low production quantities.